A great variety of rotary sprinklers are known in the patent literature. The following U.S. patents are believed to represent the state of the art: U.S. Pat. Nos. 6,016,972; 5,971,297; 5,647,541; 5,544,814; 5,372,307; 5,192,024; 5,172,864; 5,058,806; 4,984,740; 4,966,328; 4,944,456; 4,836,450; 4,836,449; 4,817,869; 4,796,810; 4,773,595; 4,754,925; 4,702,280; 4,637,549; 4,627,549; 4,624,412; 4,398,666; 4,198,000; 3,874,588; 4,376,513; 3,930,618; 3,874,588; 3,782,638; 3,727,842; 3,583,638; 3,567,126; 3,117,724; 2,989,248; 2,962,220; 2,582,158; 2,565,926; 2,421,551; 2,025,267; 1,593,918; RE 33,823.